1. Field
Aspects of the invention relate to a printed wiring board unit comprising a printed wiring board and an electronic part mounted on the printed wiring board.
2. Description of the Related Art
Mother boards have printed wiring boards. Packages of electronic circuit components such as LSI chip packages are mounted on the printed wiring board. The electronic circuit components are mounted with a ball grid array (BGA). The BGA is a package of solder bumps arranged in a matrix between printed wiring boards and a package substrate included in an LSI chip package. The package of solder bumps includes an array of bumps arranged along a rectangular outline of the printed wiring board.
[Patent Document 1]
    Japanese Laid-open Patent Publication No. 2004-241594[Patent Document 2]    Japanese Laid-open Patent Publication No. 2003-31614
The printed wiring boards are made of, for example, resin boards. Package substrates of the electronic circuit components are made of, for example, rectangular ceramic substrates. Thus, a thermal expansion rate of the package substrate is greatly different from that of the printed wiring board. Different thermal expansion rates occur between the printed wiring board and the package substrate during temperature changes. The difference of the thermal expansion rates peaks on diagonal lines of the package substrate. Consequently, the greatest stress is produced at a solder bump arranged at a corner of the rectangular package substrate. The stress repeatedly subjected to the solder bump eventually causes a solder crack.
Aspects of the present invention solve the issue described above. An object of the present invention is to provide a printed wiring board unit, a semiconductor package, and a connector for the semiconductor package for maintaining a connection between a printed wiring board and an electronic circuit component regardless of such stress.